## Acute Intracerebral Hemorrhage on CT ### Imaging Characteristics by Timeline | Timeline | CT Appearance | Reason | |----------|---------------|--------| | **Hyperacute (0–6 hrs)** | Hyperdense (60–80 HU) | Fresh blood with high protein content | | **Acute (6–24 hrs)** | Hyperdense with surrounding hypodense edema | Vasogenic edema develops | | **Subacute (1–3 weeks)** | Isodense to slightly hypodense | Hemoglobin breakdown; edema peaks | | **Chronic (>3 weeks)** | Hypodense cavity | Hemosiderin deposition; gliosis | **Key Point:** In the acute phase (first 6 hours), blood appears **hyperdense** on non-contrast CT due to the high atomic number of iron in oxyhemoglobin. The surrounding low-density (hypodense) halo represents **vasogenic edema**, which develops as blood-brain barrier disruption occurs. **High-Yield:** The hyperdense core with hypodense rim is the **classic sign of acute ICH** and helps distinguish it from acute ischemic stroke (which appears hypodense or isodense initially). **Clinical Pearl:** Mass effect (midline shift, ventricular compression) may be present even in the first 6 hours if the hemorrhage volume is large (>30 mL). ### Why This Matters - Acute hyperdensity allows rapid diagnosis without contrast - Absence of hyperdensity in suspected ICH suggests older hemorrhage or alternative diagnosis - Edema progression guides clinical deterioration risk 
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